Differences in Multi-Phase Hydrocarbon Accumulation and Controlling Factors Between Eastern and Western Kuqa Depression

The Kuqa Depression in the Tarim Basin is a structurally complex foreland basin with strong east–west variations in tectonic deformation, pressure regime, and petroleum system evolution, making reconstruction of multiphase hydrocarbon charging essential for deep and tight reservoir exploration. This study aims to compare the timing, phases, and controlling factors of hydrocarbon accumulation in the eastern Dibei area and the western Qiulitage structural belt. Petrography, fluid inclusion petrography, fluorescence spectroscopy, microthermometry, laser Raman spectroscopy, and burial–thermal history modeling were integrated to reconstruct hydrocarbon charging and pressure evolution in two representative structural domains, the eastern Dibei area and the western Qiulitage structural belt. The results show that the Jurassic Ahe Formation in the eastern Dibei area experienced four charging episodes at 22–20 Ma, 12–10 Ma, 9–7 Ma, and 3–2 Ma, including two oil-charging and two gas-charging stages, whereas the western Tuotan-1 area recorded only two main oil-charging events at 23–20 Ma and 5–3 Ma. These contrasting accumulation histories are primarily controlled by differences in the degree of tectonic contraction, pressure evolution, and source rock maturity. In the eastern Kuqa Depression, intense Himalayan compression promoted overpressure development (pressure coefficient 1.5–1.7), facilitating vertical hydrocarbon migration along fault systems and ultimately leading to tight gas accumulation following reservoir densification at ~8 Ma. In contrast, the western region experienced weaker deformation and near-normal pressure conditions, favoring lateral migration along unconformities and the formation of conventional oil reservoirs. These results highlight the role of tectonic–pressure coupling in governing multi-phase hydrocarbon accumulation and provide a geological basis not only for exploration of deep and tight reservoirs in the Kuqa Depression, but also for evaluating reservoir preservation, overpressure-related development risk, and possible hydrocarbon phase and product-quality variation.